getKeys method
Will get a collection of PcoServicesKey objects (expecting many)
using a path like this: https://api.planningcenteronline.com/services/v2/songs/1/arrangements/1/keys
Implementation
Future<PcoCollection<PcoServicesKey>> getKeys(
{PcoServicesKeyQuery? query}) async {
query ??= PcoServicesKeyQuery();
var url = '$apiEndpoint/keys';
return PcoCollection.fromApiCall<PcoServicesKey>(url,
query: query, apiVersion: apiVersion);
}